This invention relates to an apparatus for subdividing analog periodic signals, such as analog scanning signals or measurement signals which are generated by an incremental measuring instrument which scans a structured division, such as a grid scale, to measure the relative position of a first object with respect to a second object.
The resolving capacity of such measuring instruments is determined by the grid constant of the division used. A number of different approaches have been employed in the prior art to achieve smaller digital steps than the grid constant of the division in use, particularly by electronic processing of measurement signals generated by incremental measuring instruments.
One approach to such interpolation or subdivision of measurement signals is shown in Swiss Pat. No. 407,569. In this approach, the analog measurement signals, which are phase shifted with respect to one another, are applied to a resistance chain that includes a series of adjustable potentiometers. By tapping the potentiometers, a plurality of secondary signals can be generated from the primary measurement signals. Each of these secondary signals lies between the primary signals, and thus can be used to form an interpolated position value by means of a respective trigger circuit. In this interpolation system a large number of trigger circuits are required.
Another approach of the prior art is disclosed in West German DE-OS No. 27 29 297, which proposes the calculation of interpolation values with the aid of a micro-computer from digitized analog signals corresponding to the analog measurement signals. In this approach, the computing time of the micro-computer determines the maximum speed of movement which can be used with the measuring instrument.